ISO 18373-2:2008
(Main)Rigid PVC pipes — Differential scanning calorimetry (DSC) method — Part 2: Measurement of the enthalpy of fusion of crystallites
Rigid PVC pipes — Differential scanning calorimetry (DSC) method — Part 2: Measurement of the enthalpy of fusion of crystallites
ISO 18373-2:2008 specifies a method for the determination of the enthalpy of fusion of crystallites in rigid PVC pipe samples. The method is based on the measurement of the thermal history using differential scanning calorimetry (DSC) and is suitable for all types of rigid PVC pipes.
Tubes rigides en PVC — Méthode utilisant la calorimétrie différentielle à balayage — Partie 2: Mesurage de l'enthalpie de fusion des cristallites
General Information
Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 18373-2
First edition
2008-02-15
Rigid PVC pipes — Differential scanning
calorimetry (DSC) method —
Part 2:
Measurement of the enthalpy of fusion of
crystallites
Tubes rigides en PVC — Méthode utilisant la calorimétrie différentielle à
balayage —
Partie 2: Mesurage de l'enthalpie de fusion des cristallites
Reference number
ISO 18373-2:2008(E)
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ISO 18373-2:2008(E)
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ISO 18373-2:2008(E)
Contents Page
1 Scope . 1
2 Terms and definitions . 1
3 Symbols and abbreviated terms . 2
4 Principle . 2
5 Apparatus . 2
6 Preparation of the test pieces . 2
7 Procedure . 3
8 Expression of results . 3
9 Test report . 5
Annex A (informative) Possible presentations of DSC curves . 6
Annex B (informative) Example of peaks due to the presence of additives . 8
Annex C (informative) Possible sources of error . 9
Annex D (informative) Correlation between enthalpy of fusion and processing temperature . 10
Bibliography . 11
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ISO 18373-2:2008(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International
Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 18373-2 was prepared by Technical Committee ISO/TC 138, Plastics pipes, fittings and valves for the
transport of fluids, Subcommittee SC 5, General properties of pipes, fittings and valves of plastic materials and
their accessories — Test methods and basic specifications.
ISO 18373 consists of the following parts, under the general title Rigid PVC pipes — Differential scanning
calorimetry (DSC) method:
— Part 1: Measurement of the processing temperature
— Part 2: Measurement of the enthalpy of fusion of crystallites
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ISO 18373-2:2008(E)
Introduction
Studies have been undertaken at the international level to determine a method of measuring the enthalpy of
fusion of crystallites produced during the processing of rigid pipes. These studies have demonstrated that a test
using differential scanning calorimetry (DSC) fulfils these requirements.
The method involves taking small samples from the pipe wall and heating these in a differential scanning
calorimeter. Small endotherms are used to detect the thermal history of the samples and the enthalpy of fusion
of crystallites is derived from these data.
The technique requires a good understanding of DSC instruments and techniques, particularly in relation to
PVC. It is important that newcomers to the technique familiarize themselves with both the instrumentation and
method prior to undertaking reportable tests.
This method is given as a guide and no specific requirement is given in this part of ISO 18373 for the enthalpy
of fusion.
The method can also be suitable for other types of extruded rigid PVC products, but different sampling protocols
might be required.
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INTERNATIONAL STANDARD ISO 18373-2:2008(E)
Rigid PVC pipes — Differential scanning calorimetry (DSC)
method —
Part 2:
Measurement of the enthalpy of fusion of crystallites
1Scope
This part of ISO 18373 specifies a method for the determination of the enthalpy of fusion of crystallites in rigid
PVC pipe samples. The method is based on the measurement of the thermal history using differential scanning
calorimetry (DSC) and is suitable for all types of rigid PVC pipes.
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1
curve magnification
magnification of the DSC curve around A-onset and B-onset temperature (“zooming”)
2.2
A-onset
〈enthalpy of fusion measurement〉 first indication of “secondary” crystallite melting
2.3
B-onset
T
p
indication of maximum processing temperature
2.4
enthalpy of fusion
A-endotherm
∆H
A
fusion enthalpy of the secondary crystallites in the pipe
NOTE Enthalpy of fusion is expressed in joules per gram.
2.5
instrumental baseline
measurement with empty sample pan, i.e. background subtraction
2.6
position of sample
location in the product from where the sample was taken
2.7
purge gas
gas used to ensure an inert environment
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ISO 18373-2:2008(E)
2.8
repeat samples
samples from the same position
3 Symbols and abbreviated terms
DSC differential scanning calorimetry
T maximum temperature reached by the melt during processing
p
∆H enthalpy of fusion
A
4Principle
DSC is a well-established method for testing the enthalpy of fusion, ∆H , or A-endotherm, in PVC products
A
(see References [1] and [2]). The enthalpy of fusion depends upon processing conditions used to make the pipe
and an optimum value reflects a well-processed pipe which will have optimum mechanical properties.
The benefits of this test are that an accurate assessment can be made of the enthalpy of fusion, as well as the
possibility of finding variations in local areas of the product, due to the fact that only a small size of sample is
required for the test. This enables the operator to cut samples from different locations around the pipe
circumference. Thus, variations in the enthalpy of fusion in the pipe wall may be examined.
The characteristic A-endotherm occurs because secondary crystallites produced during the cooling phase after
extrusion of the pipe will melt as the sample is heated, absorbing the latent heat of fusion of these crystallites as
they do so.
5 Apparatus
5.1 DSC instrument, and associated software, calibrated.
NOTE Calibration should be carried out using at least two different metals. An instrumental baseline must be obtained with
an empty sample pan and r
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